1. Field of the Invention
The present invention relates to a webbing wind-up force limiting apparatus for use in a seatbelt system for a vehicle designed to protect an occupant in an emergency situation of the vehicle, the apparatus being capable of appropriately limiting the force applied to an occupant restraining webbing in order to wind it up.
2. Description of the Related Art
In general seatbelt systems for vehicles, a webbing for fastening the body of an occupant is wound up into a retractor, and this involves the problem that a resilient member for winding up the webbing causes the occupant to feel pressure from the webbing.
To solve such problem, there have heretofore been proposed various webbing wind-up force limiting apparatuses designed to prevent the webbing wind-up force from acting on the webbing when the occupant has it fastened, or to reduce the webbing wind-up force when the occupant is in a webbing fastened condition.
This type of webbing wind-up force limiting apparatus is generally arranged such that a pair of webbing take-up resilient members are connected together through a gear wheel, and after the occupant has fastened the webbing, a pawl is engaged with the gear wheel to lock the latter from rotating, and the biasing force from one resilient member alone is transmitted to the webbing (see, for example, Japanese Utility Model No. 129653/1984).
However, the webbing wind-up force limiting apparatus of the type described above suffers from the following problems. When the occupant unfastens the webbing and the gear wheel is allowed to rotate, a relatively strong biasing force is transmitted from one resilient member to the other, causing the gear wheel to rotate rapidly, and as the resilient member which has a relatively strong biasing force is rapidly unwound, the resilient member which has a relatively weak biasing force is rapidly rewound, and this leads to generation of noise.
A seat belt retaining and winding device for overcoming such problems has been proposed in U.S. Pat. No. 4,162,772. However, the device has a complicated structure, which results in increase in manufacturing cost and manufacturing steps.